check the ms kb Article ID: Q217210
on how to install a multi boot system.
right now I would delete the windows folder and the program files folder of win98(assuming that each os is installed on the seperate folder.)
that would leave only w2k on the second folder.
Than I would edit the boot.ini to remove the section refering to win98.
So as far as the os is concerned you have 1 os thats w2k on the second partition.
After that I would install xp on the first partition.
(if you have a 3th partition you could use that to install xp, and c would be the data).
By deleting the windows folder and the program files of win98 and removing the section from the boot.ini you will get rid of win98.
regards,
leopold